Generally, a fullerene is configured to have a hollow molecular about 1 nm in diameter, and the molecular comprises more than 60 carbon atoms connected in a basket shape. For example, C60, which more than 60 carbon atoms are connected, forms a globular molecular shaped in a soccer ball about 0.7 nm in diameter.
The fullerene in such a mechanism is known to have specific electrochemical properties, mechanical properties, optical properties, and gaseous adsorption properties. Also, the fullerene is highly expected to be applied as a new functional substance in various fields, such as electronics, life science, and agricultural and livestock industries.
Especially, it is attractive to apply the fullerene in the field of life science.
Use of photodynamic therapy agent requires its capability of efficiency for generating active oxygen by the feeble light, and its low toxicity to human body.
C60 has extremely high quantum yield (φ=0.96) of generating singlet oxygen, compared to other representative photosensitizer such as methylene blue (φ=0.52), rose bengal (φ=0.83), and eosin (φ=0.57) etc. Furthermore, it is estimated that C60 has no toxicity to human body. Therefore, it is highly expected that C60 is applicable to the photodynamic therapy agent.
However, it was difficult to administer C60 inside the body due to the fact that C60 was insoluble and had low-dispersibility in water. A lot of methods for dissolving or dispersing a fullerene in water had been previously disclosed.
Especially, a method for chemically-modifying a fullerene by water-soluble macromolecules described in Japanese Patent Publication No. H9-235235, a method for preparing a fullerene by clathrate compounds, such as Cyclophanes, Cyclodextrin, and Calix-[8]-arene described in Japanese Patent Publication No. H7-206760 and No. H8-3201, and a method for removing a organic solvent such as benzene, toluene, and tetrahydrofuran, in which fullerene is dissolved to be mixed-up with water (solvent exchange method) described in Japanese Patent Publication No. 2001-348214, and Non-Patent document titled “G. V. Andrievsky, V. K. Klosevuch, A. B. Bordyuh, G. I. Dovbeshko, Comparative analysis of two arueous-colloidal solutions of C60 fullerene with help of FTIR reflectance and UV-Vis spectroscopy, C. P. L. 364. 8-17 (2002)” are representative and well-known.
However, there is each problem in the prior arts as mentioned above.
In the first method, more specifically, in the method for modifying a fullerene by water-soluble macromolecules, there is a concern that specific physical properties of fullerene may be changed due to the chemical modification, in which may result in the expression of the carcinogenicity.
In the second method, more specifically, in the method for preparing fullerene by clathrate compounds such as Cyclophanes, it requires very complicated operation, and is impossible to obtain a pure fullerene suspension.
Using the third method, more specifically, a method for removing an organic solvent such as benzene in which a fullerene is dissolved to be mixed-up with water, many researchers have attempted to prepare various suspension, and they release a bunch of tractates. But, in the tractates, it is pointed out that the residual of the organic solvent is remained. Adjustment of the suspension by the method is acted, and various tractates are released. But, it is pointed out that the residual of the organic solvent is remained.
The methods for dissolving or dispersing a fullerene in water have been well known. However, in each of the prior methods, there are problems as mentioned above. Therefore, the fullerene suspension obtained by the methods was only applied in the limited fields. Especially, it was difficult to apply in a photodynamic therapy agent used in the field of medical and pharmaceutical science. It was also difficult to apply in the field of foods and environment.
In order to overcome these problems in the prior art, the present invention provides a method for producing fullerene suspension having high dispersion stability without any chemical compounds. Also, the method for producing the fullerene suspension makes it possible to be applied in various fields including the field of medical and pharmaceutical science and the field of foods and environment, in which the fullerene suspension obtained by the prior methods had not been applied.